Acrylic resins have found applications in a variety of fields such as signboards, shades for lighting apparatuses and lenses, due to their excellent transparency and durability. While acrylic resins are hard to break as compared with glasses, sometimes they break depending on conditions and methods of use. Therefore, there has been a continuous demand for improving toughness of these resins.
Various methods have been known as methods for improving toughness of acrylic resins. For example, the Japanese Patent Application Laid-Open No. (JP) 62-13968-B, corresponding to the U.S. Pat. No. 4,287,317, discloses a process for continuously producing rubber-modified methyl methacrylate-based syrup. According to the disclosure, the syrup obtained in this process is suitable for polymerizing by cell-casting method to give an impact-resistant methacrylic resin plate.
The process, described by JP-62-13968-B (corresponding to the U.S. Pat. No. 4,287,317), in which the rubber-modified methyl methacrylate-based syrup is produced by a continuous bulk polymerization and poured into a cell to give a methacrylic resin plate (cell-casting method), is certainly a method suitable for producing a methacrylic resin plate having a high impact-resistance. This process, however, has many disadvantages from the industrial viewpoint, such that an apparatus for large-scale continuous bulk polymerization is needed and the conditions for continuous bulk polymerization have to be controlled in order to obtain a resin with a constant quality.